To conduct the HPTN 067 clinical trial at CDC (NCHHSTP) clinical research sites in Bangkok, Thailand to achieve accrual targets. HPTN 067 is sponsored by NIMH Division of AIDS Research and the NIAID-funded HPTN Clinical Trials Network, and is currently being conducted by extramurally funded clinical research sites of NIAID (DAIDS) grantee, the HIV Prevention Trials Network (HPTN). It is expected that the CDC (NCHHSTP) clinical research site(s) will recruit HIV negative MSM from the Bangkok MSM Cohort Study, an ongoing prospective study of 1000 HIV negative MSM at the Silom Community Clinic. If the NCHHSTP Clinical Research Site(s) experience (s) difficulty in achieving these milestones, NCHHSTP staff will collaborate with NIAID (DAIDS) to develop feasible solutions. Other projects may be added to this agreement with written mutual consent of both parties.